PREBECK: We have people go out and hide something and then they post the latitude and longitude on a website - geocaching.com is the primary one - and then those of us with GPS's get the latitude and longitude from the site and go out looking for them.

SIMON: Geocaching got started around 2000 when GPS technology was made available to the general public. The very first geocache contained an odd assortment of items, including a few dollar bills, a can of black-eyed peas and a book by Ross Perot. Dave Prebeck teaches classes on geocaching and he offers his students advice, like...

PREBECK: Don't reach into holes in trees without at least rattling something around in there first. Serious. I've seen things run out of holes that have just scared the bejesus out of me.

(LAUGHTER)

SIMON: Mr. Prebeck knows a man that was bitten by a copperhead snake. But such dangers don't deter the estimated five million cachers worldwide who are on the hunt for some two million hidden sites.

PREBECK: I actually found a cache on the top of Mount Vesuvius in Italy and, I mean, just being there and seeing that and being part of that was quite an experience.

SIMON: Dave Prebeck sharing his enthusiasm on this International Geocaching Day. Happy geohunting.